Kuroe Akaishi is an introverted and quiet high school girl who appears normal. Used to solitude, her dull days start to change when she meets Arata Minami, a bright and handsome boy in her class. Despite being popular, he kindly reaches out to her, and Kuroe soon feels her heart racing around him. That racing escalates until Kuroe transforms into a monstrous kaijuu! She suffers from a peculiar condition: as her embarrassment increases, monstrous appendages sprout from her body, and when it reaches a peak, she fully transforms. Meanwhile, beauty encounters the kaijuu, and Japan faces the threat of this mysterious monster. Can Minami accept her feelings, or will her colossal form frighten him away? His decision could lead to the devastating consequences of a girl's heart-pounding, youthful love.